Respiratory - Noninfectious Pulmonary Parenchymal Disease

Question 1

What happens when Carbon monoxide (CO) is inhaled?

Answer 1

• Forms Carboxyhemoglobin
  
  • CO has 200x greater affinity for hemoglobin
  • Less O₂ carried in blood
  • Less O₂ released at tissues (holds on tight)
• Mucus membranes can be red but oxygen is not as available to tissues

Question 2

What is Cyanide Toxicosis?

Answer 2

• Produced by combustible items as they burn
• Cyanide inhibits cytochrome oxidase
  
  • inhibits aerobic metabolism
• CNS and heart depend on aerobic ATP production
• Almond odor

Question 3

What are the respiratory concerns with fire patients?

Answer 3

• Tissue Hypoxia:
  
  • ⇣ inspired, carrying, and release of O₂
  • Cardio (arrhythmias), Neuro (sedate, seizures, coma)
• Thermal Damage
  
  • Upper respiratory tract and larynx
  • Dermal burns
• Pulmonary Irritation
  
  • Toxins cause chemical or thermal-induced bronchoconstriction, inflammation, necrosis, pulmonary edema
  • Signs range from ⇡RR to fatal respiratory dysfunction

Question 4

What can be seen on radiographs of fire patients?

Answer 4

• Can be normal in mild cases (20%)
• Can show bronchial disease from toxin irriation
• Can show pulmonary edema
  
  • inflammation and oxidant injury damage alveoli and increase permeability
  • blood flow increased and lymphatics impaired
• Can show alveolar pattern
  
  • pneumonia can occur after smoke inhalation

Question 5

What are the treatments for Fire patients?

Answer 5

• Respiratory Tract:
  
  • O₂ supplementation to eliminate CO
    
    • hyperbaric oxygen chamber can help
  • Bronchodilators
  • Nebulization and coupage
  • Other potential therapies
    
    • Antibiotics if documented pneumonia
    • Steroids if obstructive airway edema/inflammation
    • Tracheostomy f obstruction
    • +/- mechanical ventilation
  • Burns: wound care, antibiotics, IV fluids, analgesia
  • Eyes: Topical antibiotics and atropine

Question 6

What does a Hyperbaric Oxygen Chamber do?

Answer 6

• Patient breathes 100% Oxygen intermittently inside a chamber with increased pressure
  
  • More O₂ dissolved in blood
  • ⇡ availability to tissues (12-15x)
  • Allows CO elimination too

Question 7

What is Pulmonary edema? causes?

Answer 7

• Pulmonary Edema = increased fluid in the extravascular pulmonary parenchyma
  
  • Cardiogenic (congestive heart failure)
    
    • increased hydrostatic pressure due to falling heart and fluid overload
    • Non-cardiogenic
      
      • increased permeability of vessels from damage to microvascular barrier, causes leaking fluid and protein into interstitium and alveoli

Question 8

What is the clinical presentation of Pulmonary edema?

Answer 8

• Dyspnea, cough
  
  • may cough up pinkish foam
• Harsh and moist sounding lungs (crackles)
• listen closely for murmur

Question 9

How should a patient with pulmonary edema be radiographed?

Answer 9

• DV less stressful than VD
• Have oxygen available

Question 10

What are the differentials for Noncardiogenic Pulmonary Edema?

Answer 10

• Stepwise Diagnostics as needed O₂ in between
  
  • Radiographs confirm edema and help with cardiac/noncardiogenic
  • Echo to confirm/ruleout cardiac disease if in question
  • Hx ad PE help prioritize/ruleout many noncardiogenic differentials
    
    • Oral ulcerations - think electrocution
    • Signs of infection/sepsis - CBC, Chem, cultures, titers
    • Non of the above? - is there systemic inflammation, neoplasia, neurologic disease

Question 11

What is the treatment for noncardiogenic pulmonary edema?

Answer 11

• Oxygen and low stress
• Treat underlying disease
• Furosemide:
  
  • helps if cardiac edema (congestive heart failure)
  • Ok to try 1 dose while sorting out reason for edema
  • willl not help noncardiogenic edema cases
    
    • may be harmful if patient is hypovolemic
• Ventilator for severe cases

Question 12

What is Acute Respiratory Distress Syndrome (ARDS)?

Answer 12

• Exaggerated inflammatory response in the lungs
  
  • sequelae to acute lung injury, systemic inflammation or sepsis
  • Cytokines infiltrate, chemotaxis of neutrophils and macrophages
  • Permeability of pulmonary vessels keeps increasing
    
    • Non-cardiogenic edema worsens

Question 13

What is Pulmonary Thromboembolism?

Answer 13

• Obstruction of a pulmonary vessel with a blood clot originating at some distant site
• Risk factors:
  
  • Virchow’s Triad-
    
    • vascular injury
    • Impaired blood flow (stasis)
    • hypercoagulability

Question 14

What conditions result in hypercoagulable patients?

Answer 14

• Protein losing nephropathy/enteropathy
• Immune mediated hemolytic anemia
• Neoplasia
• Necrotizing pancreatitis
• Cushing’s and steroid patients
• Diabetes mellitus
• Sepsis
• Trauma
• Cardiac Disease - not truly hypercoagulable, but ⇡ risk for emboli
  
  • heartworm, endocarditis, cardiomyopahty

Question 15

What happens to pulmonary thromboembolisms?

Answer 15

• Normal coagulation - clot starts lysing within several hours
• Abnormal coagulation - existing clots can grow and more clots can form and travel

Question 16

What are the clinical signs of Pulmonary Thromboembolism?

Answer 16

• Vary from subclinical to acutely fatal
• Acute onset dyspnea, tachypnea
  
  • Ventilation/perfusion mismatch
  • Hypoxia
• Signs of underlying disease elsewhere

Question 17

How is pulmonary Thromboembolism diagnosed?

Answer 17

• Often suspected but hard to prove
• Chest Radiographs
  
  • areas of hypovascular lung (VD/DV views)
  • Pulmonary infiltrates (hemorrhage, atelectasis, infarct)
• Coagulation Testing
  
  • PT/PTT/platelets - no correlation between these and thromboembolism
  • Low antithrombin III concentration increases thrombotic risk
  • Higher D-Dimer concentration is consistent with PRE
    
    • D-dimer = plasmin-mediated break
• Try to confirm with:
  
  • pulmonary angiography
  • Nuclear scintigraphy

Question 18

What is the treatment for Pulmonary thromboembolism?

Answer 18

• Oxygen supplementation
• IV fluids to optimize perfusion
• Bronchodilator may help
  
  • Theophylline ⇢ pulmonary vasodilation
• Prevent more Clots
  
  • Heparin 100 U/kg SQ TID
  • Aspirin 0.5-1.0mg/kg PO q24hrs
  • Clopidogrel 0.5-1mg/kg PO q24hrs
• Treat underlying disease

Question 19

What are pulmonary contusions

Answer 19

• Compression injury w/hemorrhage
  
  • injury to vessel walls causes non-cardiogenic edema and loss of lung compliance
• Can be progressive in first 24-48hrs
  
  • may present with decent or good respiratory function
  • Can deteriorate quickly
  • if survive - resolve over 7-10days
• most common thoracic injury in dogs/cats
  
  • Car accidents, falls, fights, abuse

Question 20

What are the clinical signs of pulmonary contusions

Answer 20

• Can be mild at first
• Then tachypnea, dyspnea, open-mouth breathing
• Crackles, cyanosis, hemoptysis, ⇡HR, arrhythmias

Question 21

How are pulmonary contusions diagnosed?

Answer 21

• Radiographs- patchy alveolar or interstitial pattern
  
  • may take 48hrs to appear
    
    • CT documents changes earlier

Question 22

What is the treatment for Pulmonary Contusions?

Answer 22

• Treat life-threatening injuries
• Oxygen supplementation
• Pain control
• Fluids to optimize perusion, but avoid fluid overload
  
  • may have increased vascular permeability ⇢ non-cardiogenic pulmonary edema
• Monitor closely for 48hrs (may worsen quickly)
• Ventilator for severe cases

Question 23

What is the pathophysiology of Lung lobe torsions

Answer 23

• Lung torses and vein collapses but artery stays open
  
  • severe congestion causes fluid to leak into interstitium
  • lung consolidates, fluids leaks out, pleural effusion forms
• Why?
  
  • Spontaneous, underlying respiratory disease, surgical trauma
    
    • Anything that causes consolidation or atelectasis in cobco with extra fluid or air surrounding the lobe could increase risk of torsion

Question 24

Which breeds have an increased risk of lung lobe torsions?

Answer 24

• Large deep-chested dogs
  
  • Afgan hound 133x more likely than other breeds
• Pugs increased risk

Question 25

What is the clinical presentation of patients with lung lobe torsion?

Answer 25

• Dyspnea
• coughing
• depression
• Dull lung sounds due to consolidation and effusion

Question 26

How is Lung lobe torsion diagnosed?

Answer 26

• Thoracocentesis to improve breathing, fluid analysis
• Radiographs - consolidation with air bronchogram
  
  • right middle or left cranial lobes (due to shape and looseness)
• Ultrasound w/ Doppler: torsed hilus obstructed with fluid and lack of venous flow
• Fluid Analysis (variable)
  
  • Clear
  • Serosanguinous/hemorrhagic
  • Chylous
  • Cytology:
    
    • neutrophils and lymphocytes
    • check for neoplasia and fungal disease
  • Culture usually negative

Question 27

What is the treatment for lung lobe torsion?

Answer 27

• Remove fluid prior to surgery
  
  • Some dogs need chest tubes
  • Oxygen and IV fluids as indicated
• Sx for lung lobectomy

Question 28

What is the prognosis for patients with lung lobe torsion

Answer 28

• Most dogs do well if spontaneous or non-neoplastic
• Afgans ⇡ risk for persistent chylothorax post-op

Question 29

What is the common signalment of Pulmonary Fibrosis patients?

Answer 29

• Middle to older age dogs and cats
• No sex predilection
• Breeds:
  
  • West highland white terriers
  • Staffordshire bull terriers
  • Other terrier breeds
  • Miniature poodles
  • No specific cat breeds

Question 30

What is the Etiology of Pulmonary Fibrosis?

Answer 30

• Primary Idiopathic
• Genetic predisposition
• Secondary
  
  • infectious
    
    • FIV, herpes, calicivirus, toxoplasmosis, histoplasmosis, COVID
  • Toxin- paraquat is a classic offender
  • Neoplasia
  • Systemic lupus erythematosus

Question 31

What is the pathophysiology of Pulmonary Fibrosis?

Answer 31

• Damage to alveolar epithelium and Type I pneumocytes
• Type II pneumocytes are more compact and less sensitive to injury - so they proliferate to fill in denuded areas

Question 32

What is the history and PE associated with Pulmonary Fibrosis?

Answer 32

• Hx:
  
  • usually slowly progressive respiratory signs
    
    • BAR, good appetite
    • Exercise intolerance, tachypnea, dyspnea, cough
• PE:
  
  • Abnormal auscultation
    
    • Crackles common, wheezes may be present

Question 33

How is Pulmonary Fibrosis diagnosed?

Answer 33

• Radiographs
  
  • pronounced patchy diffuse pattern
  • Equal number of interstitial, alveolar, bronchial patterns; some mixed
• Investigate other differentials or triggers that may be treatable (infectious) or not so treatable (neoplasia, paraquat)
• Echo: may have pulmonary hypertension that we can treat
• CT: classic honeycomb appearance in people
• Lung aspirate:
  
  • not very helpful, unless able to assess architectural changes or degree of fibrosis
  • helps ID other diseases (cancer, fungal)
• Lung biopsy:
  
  • Gold standard, but not always definitive
  • Patchy distribution means you can miss it
• Dx is often presumptive based on breed and consistent signs and findings

Question 34

What is the treatment for Pulmonary Fibrosis?

Answer 34

• Supplemental oxygen as needed
• Immunosuppressive therapy (steroids, azathioprine - dogs only)
• Anti-fibrotic therapy (steroids, +/- -colchicine)
• Anti-pulmonary hypertension (sildenafil)

Question 35

What is Pulmonary Hypertension? Why does it occur?

Answer 35

• Increase in pulmonary arterial pressure
• sources:
  
  • ⇡ left atrial pressure
  • Pulmonary over-circulation
  • ⇡ pulmonary vascular resistance

Question 36

What leads to pulmonary hypertension?

Answer 36

• Severe respiratory disease
  
  • Decreased oxygen exchange ⇢ Hypoxia
  • Hypoxia ⇢ vascular constriction and hypertrophy of pulmonary arterial walls
• Underlying respiratory causes
  
  • Fibrosis, pneumonia, chronic bronchitis
  • Also seen with PTE, HW, shunts, mitral disease

Question 37

What are the clinical signs of pulmonary hypertension

Answer 37

• Cough
• Dyspnea
• Cyanosis
• Collapse

Question 38

What are the diagnostic tests for pulmonary hypertension

Answer 38

• Thoracic radiographs - assess lungs for primary respiratory disease
• Echocardiogram is most practical way
  
  • measure increased pulmonary artery pressure

Question 39

What is the treatment for Pulmonary Hypertension?

Answer 39

• Sildenafil to relax pulmonary vasculature

Question 40

What primary lung tumors are found in dogs? signs? treatment?

Answer 40

• Single mass, often incidental finding
• Usually carcinomas, spread locally
• Clinically normal or cough, dyspnea, hemoptysis
• Often can be surgically removed

Question 41

What primary lung tumors are found in cats? signs? treatment?

Answer 41

• Bronchogenic carcinomas, metastasize to digits
• Radiographs extremely variable
• Present with progressive dyspnea, increased effort